This document provides the Commission's recommendations for the design of individual monitoring programmes and the interpretation of results of measurements of intakes of radionuclides by radiation workers. It follows the Commission's general principles of monitoring for radiation protection of workers (ICRP, 1977a) and should be used in conjunction with those principles. The main objective of the document is to give specific guidance on the design of monitoring programmes, the calculation of derived reference levels and the interpretation of monitoring results. Since models are required to provide a link between the measured quantity and the appropriate limits or reference levels, the document also gives general guidance on the models used. Finally, specific values of derived reference levels are given for radionuclides chosen for their potential importance in occupational exposure; these levels have been calculated for intake by inhalation only since this is the most likely route of intake. The Commission wishes to emphasis that the parameters used and the reference levels calculated in this document are appropriate for occupationally exposed adults only and that they are not intended to be used to evaluate exposure for members of the general public.